In emergency situations, hydraulic and other power systems require a manual override of valve positions. FIG. 1 shows an example of a manual override device 10 for changing the positions of spools 12 so as to provide different flows and pressures through first and second ports 16 and 17. A first end 21 of an extension rod 20 is securely attached within a channel 13 of the spool 12 and a reduced diameter section 23 and a ball end 25 are provided at the second end 22 of the rod 20 for connection to a lever 14. The lever 14 is can be moved to manually change the positions of the spools 12. A seal housing 30 attached to the body 32 of the hydraulic power system beneath each spool 12 retains a conical spring 28 that is biased against the spool 12. The rod 20 passes through the seals 26 of the housing 30. During ordinary operation (as used herein, ordinary operation means under normal operating conditions in which no manual override is active) of the hydraulic power system 1 shown in FIG. 1, the rods 20 move together with the spools 12 and therefore also move with respect to the surrounding seals 26 and the lever 14.